Satellite systems supporting multiple missions require operation over multiple frequency bands. Separate antenna apertures cannot be used for each frequency band, due to the limited real estate on the satellite, so antennas must operate over multiple frequency bands.
Reflector antennas are often used on satellites for their mass efficiency and consist of one or more reflectors and feeds. Reflectors are inherently broadband, but multi-frequency feeds are complex and difficult to design and build. Using separate feeds for each frequency band reduces the feed complexity, however, when the feed is displaced from the reflector focal point, the beam is scanned from the mechanical boresight of the system and the gain of the antenna is reduced (called scan loss) resulting in degraded system performance.
Multi-frequency feed systems and frequency selective surfaces have been used to provide limited multiple frequency operation. Separate feeds operating at each frequency located side-by-side have also been used. Both of these systems have problems.
Multi-frequency feed systems are complex and difficult to build. Only a few feed systems have been developed for two or three frequency bands and are highly dependent on the frequency plan. If the frequencies are too close or the bandwidths are too broad, these feeds cannot be made to operate. Frequency selective surfaces (FSS's) have been designed to combine separate feeds to illuminate a common reflector. Like the multi-frequency feeds, FSS performance is highly dependent on the frequency plan. They also require significantly more volume and mass to implement.
Separate feeds located side-by-side is the simplest implementation with the least constraints on the frequency plan. However, when placed in conventional reflector systems, they suffer from beam scan and scan loss, as described above.
What is needed is a method and system that overcomes the above-identified issues. The present embodiment addresses this need.